Recently, a sensor device to detect various physical amounts has been developed to realize a stable operation and improved reliability of a vehicle, a mobile phone, and a digital camera. In the vehicle, particularly, an acceleration sensor and an angular velocity sensor are applied widely for apparatus (for example, an airbag) control to prevent sideslip and improve a safety of passengers. When the sensor device is applied to the vehicle, the sensor device may be mounted in an engine room. For this reason, the sensor device needs to endure a severe environment load such as a thermal change and a mechanical vibration and the sensor device needs to be miniaturized so that the device can be mounted in a limited space.
In the acceleration sensor and the angular velocity sensor mounted on the sensor device, a detection mechanism using fine processing technology of silicon (Si) is mainly used for the purpose of miniaturization, multi-functionality/complexity, and improvement of mass productivity. A minute comb-shaped structure of silicon is formed by the fine processing technology, minute displacement of the comb-shaped structure is converted into an electric signal, and physical amounts such as acceleration and angular velocity are detected.
In the sensor device in which the acceleration sensor and the angular velocity sensor are sealed with a resin and a package is formed, linear expansion coefficients of embedded members such as the sensors and a substrate configuring the package and the sealing resin are different from each other. In addition, sizes and thickness of the members such as the sensors and the substrate embedded in the package are generally different from each other and the members are often arranged with asymmetric structures in the package. If a temperature change is applied to the package, warpage deformation may occur in the package due to the difference of the linear expansion coefficients between the members and asymmetry of the structures. Due to the warpage deformation of the package, deformation (expansion/contraction and warpage) occurs in the sensor and the sensor is inclined according to the warpage of the package. If the sensor deforms or is inclined, a position changes, and then stress occurs in the sensor. As a result, the comb-shaped structure in the sensor also deforms and a detection signal is output even in a state in which inertial force such as the acceleration and the angular velocity does not act addition a detection range of the inertial force is narrowed and reliability of the sensor device is greatly decreased. Therefore, in the sensor device in which the fine processing technology of the silicon is applied to a detection mechanism of the inertial force such as the acceleration and the angular velocity, it is necessary to realize a package structure that does not cause the position change such as the deformation, and the inclination in the packaged sensor.
An example of a sensor device in which an acceleration sensor and a pressure sensor are sealed with a resin and a package (mold body) is formed is disclosed in PTL 1. In the sensor device disclosed in PTL 1, the acceleration sensor, the pressure sensor, and a signal processing circuit are arranged on a lead to form a line in a transverse direction (plane direction) of the package and the acceleration sensor and the pressure sensor are arranged at almost symmetrical positions with respect to a center of the signal processing circuit. In technology disclosed in PTL 1, to reduce thermal stress occurring in a physical amount sensor due to a difference of linear expansion coefficients of the physical amount sensor and the mold body made of a plastic material, the following configuration is adopted. That is, a mold body thickness between the physical amount sensor and a surface of the sensor-side mold body and a mold body thickness between the lead and a surface of the lead-side mold body are almost equalized. Or, a volume of a portion covering a top surface side of the lead of the mold body and a volume of a portion covering a bottom surface side of the lead of the mold body are almost equalized.
In addition, an example of a semiconductor device to decrease stress received by a semiconductor chip sealed with a resin is disclosed in PTL 2. In the semiconductor device having a tape carrier package structure disclosed in PTL 2, both a principal surface and a back surface of the semiconductor chip thinner than a tape carrier are sealed with the sealing resin. The sealed semiconductor chip is arranged at a position of a thickness direction of the tape carrier, such that a package stress neutral surface parallel to the principal surface of the semiconductor chip and a stress neutral surface of the semiconductor chip are almost matched with each other. By such an arrangement of the semiconductor chip, the stress received by the semiconductor chip can be decreased, even though the entire package deforms.